Janszky and Ljung first reported a higher incidence of AMI following the spring DST shift, which was more pronounced in women . We reviewed the available literature on this association , and found another six studies, four conducted in Europe and two in the United States, accounting for a total of 87,994 cases. Although there were differences among each other, they all supported the existence of an association between DST and the risk of AMI, particularly after the spring DST transition, with an increase ranging from 4 to 29%. In particular, three studies report a higher incidence on Monday, and only four provide an analysis by separating subgroups by gender .
The central master clock is primarily entrained by light, and reduced exposure to light during the day and over exposure to light at night due to artificial lighting may impair the circadian organization of sleep. Changes in sleep architecture during sleep disruption may lead to increased energy intake, reduced energy expenditure, and insulin resistance. Short (< 6 h) sleep has been associated with negative health outcomes including hypertension, diabetes mellitus, obesity, and even mortality. A recent study has shown that short sleep, compared with normal sleep, is associated with a significant increase in the relative risk (RR) of mortality due to all causes (RR 1.12). Moreover, short sleepers have increased rates of obesity (38%), diabetes mellitus (37%), coronary heart disease (26%), and hypertension (17%) .
Personal circadian preference (chronotype) and gender
In 1976, Horne and Ostberg published a milestone study on possible individual differences in circadian attitudes in the International Journal of Chronobiology. By means of a simple self-assessment questionnaire (Morningness–Eveningness Questionnaire, MEQ), they evaluated individual differences in the circadian variation of oral temperature. Subjects categorized as morning types (M-type) show a significantly earlier peak time than evening ones (E-type) and have a higher daytime temperature. Intermediate types (I-type) have temperatures between those of the other groups. Recently, we collected the available evidence dealing with the association between chronotype, gender, and general health . Individuals with the evening chronotype show sleep-related issues, e.g., later bedtime and wake-up and decreased sleep quality and quantity. Moreover, these people are prone to skipping breakfast, to have reduced physical activity, unhealthy dietary patterns, and other habits (smoking and alcohol), along with poor glycaemic control, metabolic syndrome, and diabetes. There are conflicting findings on whether men and women differ in their energy balance responses to sleep disruption, but women seem to be more susceptible. In particular, the female–evening association gives rise to several problems. Excessive daytime sleepiness and poor sleep quality are higher among females, and female predominance in the rate of depression is observed in subjects with a delayed sleep–wake schedule. Moreover, disturbances of the sleep–wake cycle in E-type females can also be increased by the presence of nightmares. Evening association may also be linked to being overweight, a feature that may more significantly impact the emotional health of adolescent females. Chronotype may also influence cognitive patterns and academic achievement. Evening association, in fact, can be a problem for morning attention at school, which is more evident in E-type girls compared to E-type boys .